X-ray apparatus for displaying in slow motion tissues which move with the rhythm of the heart

ABSTRACT

A method of X-ray examination of objects that move in rhythm with the heart wherein the image information is switched on and off in synchronism with the heart action. In a preferred embodiment, the high voltage supply of the X-ray tube is switched on and off at the heart frequency and is on for a period that is short compared with the duration of one heart action.

States latent: [191 Int. Cl H05g 1/00 Geratsdorfier July 23, 1974 X-RAYAPPARATUS FOR DISPLAYING IN [58] Field of Search 250/322, 401, 402

SLOW MOTION TISSUES WHICH MOVE 1 WITH THE RHYTHM OF THE HEART [56]References Cited [75] Inventor: Edmund Gerats'dorfer, Munich, UNITEDSTATES PATENTS many I 2,152,045 3 1939 Gulland 250 402 [73] Assignee:U.S. Philips Corporation, New 2,190,389 2/1940 Strauss et a1 250/322Y0rk,.N.Y. 22 F1 1 l 5 Primary Examiner-William F. Lindquist 21; A N 364 Attorney; Agent, or Firm-FrankR. Trifari pp 9 v RelatedApplicationData [57] ABSTRACT [63] g" g, i 3 g 3 A method of X-rayexamination ofobjects that move S S 6 g i zzgggzg o in rhythm with theheart wherein the image informav tion is switched on and off insynchronism with the r heart action. In a preferred embodiment, the high1 Furelgn Application Pnority Data voltage supply of the X-ray tube isswitched on and off I Dec. 17,1969 Germany 1963312 }at the heartfrequencyand is on for a p i h i U S C! d 250/322 250/401 short comparedwith the duration of one heart action. i 2 Claims, 2 Drawing FiguresPATENTEUJULZIBIHH 3,825,761

v INVENTOR. EDMUND GERATSDORFER 1 x-rrxv APPARATUS FOR DISPLAYING INsLow MOTION TISSUES'WHICI-I MOVE WITH THE RHYTHM on THE HEART This is acontinuation of application Ser. No. 281,117,'filed Aug. 16, 1972, nowabandoned, which application was a continuation of application Ser. No.a

93,089, filed Nov. 27, 1970, now abandoned.

This invention relates to a method of X-ray examination of objects thatare moved in rhythm with the heart. When examining "such objects, forexample, the tissue surrounding the heart (in thorax radiographs) orwhen examining the blood vessels, blurring due to movements is causedboth in radiographs and in X-ray screening. The lack of sharpness due tomovements in X-rayscreening is determined by the inertia of the imagetransmission system, particularly of the X-ray image intensifier and ofthe television camera tube, 'so that only a blurred representation ofrapidly moved objects can be obtaine v The lack of sharpness due tomovements in radiographs may be minimized by using theshortest possibleexposure times, but this approach is limited by the pulses supplied bythe pulse shaper 6 and the frequency of which corresponds with thefrequency'of the heart. Therefore the radiation also penetrates thepatient 1 in phase with the cardial action so that a sharp image isobtained provided that the duration of the pulses is chosen to be shortas compared with the duration of a heart action (for example, 20 msec to1 sec). The radiograph or the screening image become sharper when thepulse duration is shorter. This involves, it is true, a reduction of theradiation power of each Xray pulse, but this decrease in power can becompensated for to a given extent by an increase in the heating currentof the X-ray tube the heating current supply is not shown for the sakeof clarity particularly in X-ray screening.

It should be noted that in X-ray technology switches controlled in theheart phase are known (for example,

for heart-phase controlled stereoscopic graphs). How-' ever, inthiscase, only a single X-ray pulse per radiograph is supplied in agiven phase of the heart action. In contrast, in the present method aplurality of X-ray pulses are supplied in a single radiograph andespecially power of the X-ray apparatus. The lack of sharpness in X-rayscreening has hitherto been unavoidable.

An object of the invention is to develop a method which avoidsunsharpness due to movements in X-ray examination of organs moved in therhythm of the heart. According to the'invention this is achieved byswitching the image information on and off at least approximately inrhythm with the heart. In one embodiment of the invention the imageinformation .is switched on and off by switching X-rays on and off. Asan alternative, the image information could be switched on and off byarranging a rotating diaphragm in front of thefilm or by darkening theimage intensifier and/or the television camera tube in screening.However, this possibility is inconvenient in as much as the X-raydosagereceived by the patient is considerably increased as compared with anormal radiograph or screening.

Further details and advantages of the invention willbe described morefully with reference to an embodiment shown in the drawing, in which:

drawing only shows the cuff) and applied to an'elec- --trocariographicapparatus 3. The cardial stresses .produce, in a pulse shaper 4, a pulsesequence the periodicity of which corresponds with the'periodicity ofthe cardial action. This pulse sequence. is delayed by a delay member 5by an adjustable time interval and applied to a further pulse shaper 6,which simultaneously amplifies the pulses and which supplies atits'output pulses whose duration is-adjustable. The pulses supplied bythe pulse shaper 6 actuate during their period a switch 7 which isincluded in the primary circuit of the high-voltage transformer 8 of theX-ray tube examined object may be observed in X-rayscreening always inthe same position'of the object, which pulses are summated on the. film.In X-ray screening the dosage may be reduced by storing the image inappropriate stores (for example, magnetic recording or the like) untilthe next-following X-ray pulse.

The position of the X-ray pulses relative to a given phase of the heartaction, for example, the so-called R- peak in the electro-cariogram, maybe adjusted at will by means of the adjustable delay member 5. If thisadjustment is continuously changed during screening, the during theseparate phases of the heart action.

In some practical cases it alsois desired to examine, in X-rayscreening, the course of the movements, be it not with the actual rate.As in the case of a stroboscope this may beachieved'in that the X-raytube is driven at a pulse frequency slightly differing from the heartfrequency.

For this purpose the adjustable delay member 5 has only tov be replacedby the circuitry shown in FIG. 2, The pulses supplied bythe pulse shaper4 are applied to a known type of pulse duration modulator 10 whichproduces pulses whose duration depends upon the instantaneous value of asawtooth voltage applied to its second input and supplied by thesawtooth generator 11. If the rear flanks of these pulses are utilizedfor controlling the pulse follower 6, a sequence of pulses is obtainedafter the pulse follower 6,.the phase position of which sequencerelative to the heart action voltage depends upon the instantaneousvalue of the sawtooth voltage. By suitably proportioning the pulseduration modulator and the sawtooth generator it can be ensured that thephase shift during each leading edge of the sawtooth voltage-liesbetween a very short value and the duration of one heart action. Thecourse of the movement is than extended in time in the ratio between theheart frequency and the sawtooth frequency. Therefore the frequency ofthe sawtooth voltage has to below as compared with the frequency of theheart action voltage. It is more efficient to use a sawtooth gen- 9.Thus theX-ray tube 9 supplies X'ra-y pulses'the-duration of whichcorresponds with-the duration of "the crater of adjustable frequency sothat the expansion in time may be varied at will. The switch 7 mayeffectively be formed by a thyristor which makes it possible to use theshortest possible switching-on periods.

What is claimed is:

1. An X-ray apparatus comprising an X-ray tube, a source of high voltagefor the X-ray tube, a switch coupling said tube and voltage source forswitching the tube voltage on and off at substantially a rate which isslightly different from the heart frequency of a person underexamination, first means responsive to the heart frequency of the personfor deriving a first sequence of pulses with a repetition rate equal tothe heart frequency, second means for deriving from said first sequenceof pulses a second sequence of pulses of adjustable duration forcontrolling said switch, a delay member with a continuously variabledelay being coupled between said first and second means, and controlmeans connected to said delay member to vary the delay in apredetermined manner whereby the portion of the person being examined isdisplayed moving in slow motion for critical examination of the portionin pulses being utilized for controlling the switch.

1. An X-ray apparatus comprising an X-ray tube, a source of high voltagefor the X-ray tube, a switch coupling said tube and voltage source forswitching the tube voltage on and off at substantially a rate which isslightly different from the Heart frequency of a person underexamination, first means responsive to the heart frequency of the personfor deriving a first sequence of pulses with a repetition rate equal tothe heart frequency, second means for deriving from said first sequenceof pulses a second sequence of pulses of adjustable duration forcontrolling said switch, a delay member with a continuously variabledelay being coupled between said first and second means, and controlmeans connected to said delay member to vary the delay in apredetermined manner whereby the portion of the person being examined isdisplayed moving in slow motion for critical examination of the portionin motion.
 2. An apparatus as claimed in claim 1 wherein said delaymember and said control means connected to said delay member comprise apulse duration modulator, and a sawtooth voltage generator coupled toand controlling said pulse duration modulator so that it supplies pulseswhose duration depends upon the instantaneous value of the amplitude ofa sawtooth voltage supplied thereto, the trailing edge of the producedpulses being utilized for controlling the switch.